Secondary aspartic acid amide esters

ABSTRACT

New secondary amines are described which are prepared from inexpensive, commercially available raw materials, are stable at room temperature, and are reactive toward electrophiles. The secondary amines are prepared by the addition of one or more primary amines with one or more male (amide/ester) and fumar (amide/ester) Michael receptors. The above amines can be used as coreactants with aliphatic polyisocyanates for polyurea coatings. The novel secondary amines are also described as particularly useful as part of a two-part liquid pavement marking composition for pavement markings.

This is a division of application Ser. No. 09/109,588 filed Jul. 2,1998, now U.S. Pat. No. 6,005,062.

FIELD OF THE INVENTION

The invention relates generally to new secondary amines and their use incoatings, e.g. polyurea coatings and in a liquid pavement markingcomposition.

BACKGROUND OF THE INVENTION

Polyfunctional amines are used as coreactants with polyfunctionalisocyanates in many applications. These reactions yield polyureas whichare a highly regarded class of polymers, known for their toughness, highstrength and dynamic mechanical and high temperature performance. Thesereactions are generally carried out in specialized equipment, due to thehigh reactivity of amines and isocyanates. This has limited their use intraditional adhesives, coatings and sealer type product applications.

Typical primary and secondary amines are extremely reactive with avariety of electrophiles, which results in very short gel times withlittle or no potlife. The reaction of primary amines with isocyanates isextremely exothermic and produces strongly hydrogen bonded dihydro-urealinkages. Strongly hydrogen bonded groups may disadvantageously increaseproduct viscosities and hinder subsequent mobility and reactivity ofattached functional groups. Additionally, uncontrollable reaction ratesare undesirable in many applications.

The utility of amines of the present invention is based on the additionreaction between a polyisocyanate component and an isocyanate-reactivecomponent, in particular polyamines containing secondary amino groups.This reaction is known in principle from DE-OS 2,158,945 (Fed. Rep. OfGerman, 1973) but according to the teachings of this publication thereaction is not used for crosslinking two-component coating compositionsat relatively low temperatures but rather for the preparation ofintermediate products which are converted at elevated temperatures intoheterocyclic end products.

Bayer Corp. has recently introduced polyaspartic acid diesters under thename DESMOPHEN™. These secondary amines react more controllably withelectrophiles than do the corresponding primary amines. However, theadducts of these amines and isocyanates are capable of a furthertransformation to form a hydantoin ring structure, giving rise toshrinking of the coating and generating undesired alcohol byproducts.

U.S. Pat. No. 5,126,170 describes secondary amines, referred to as“polyaspartic acid derivatives”, which are formed by the Michael-typereaction of primary polyamines with maleic or fumaric acid ester Michaelreceptors. This reaction is illustrated below as formula (I), whereinR₁, R₂ and R₃ are as defined in the cited reference.

These aspartic ester diesters react with isocyanates to formurea-diester linkages. This reaction is illustrated below as formula(II), wherein R₁, R₂, R₃ and R₄ are as defined in the cited reference.

Urea-diester linkages are reportedly unstable however, cyclizing to thehydantoin with the concomitant expulsion of alcohol. The expelledalcohol is problematic in some systems such as isocyanate-terminatedprepolymers, since it may undesirably react with residual isocyanategroups. Dimensional changes of the polymer upon hydantoin formation is apotential problem as well. This reaction is illustrated below as formula(III), wherein R₁, R₂, R₃ and R₄ are as defined in the cited reference.

In addition to U.S. Pat. No. 5,126,170, the above aspartic esterdiesters are described to be suitable for manufacture of highperformance polyurethane or polyurea coatings for specific end-useapplications in U.S. Pat. Nos.: 5,236,741, 5,243,012, 5,412,056,5,516,873 and 5,580,945.

There is a need for improved polyurea and polyurethane coatings havingamine components that resist hydantoin formation.

There is a significant need for a liquid pavement marking compositionthat will provide increased durability and retained reflectivity onceapplied to a surface 15 and dried or cured. Furthermore, it isadvantageous to apply markings in a wider range of weather conditionsthan is possible with existing compositions. There is also a need formarking compositions with improved cure profiles to ensure bothsubstrate wet out and rapid track free time. Improvements are needed toobtain compositions that are substantially free of volatile organiccomponents. Compositions of this type are typically used on roads,highways, parking lots and recreational trails to form stripes, bars andmarkings for the delineation of lanes, crosswalks, parking spaces,symbols and legends and the like. They are typically applied by spraycoating (i.e., painting) the pavement surface. Preformed pavementmarking sheets or tapes have also been used to mark pavement or trafficbearing surfaces.

Pavement marking stripes, or pavement markings of other shapes, mayinclude reflective optical elements adhered to the pavement surface bythe use of a binder. Current traffic paint systems typically useconventional 1.5n_(D) glass microspheres for increased retroreflection.The microspheres are typically flood coated onto the wet markingimmediately after coating. This provides the paint with improvedretroreflectivity and also covers the top surface of the uncured orundried coating with a protective layer of microspheres. This protectivelayer allows the markings to be exposed to traffic sooner because of thelayer of microspheres over the surface, which prevents transfer of thecoating to the surface of vehicle tires. This is important for rates ofmarking application. The time between application and the point wherematerial will no longer transfer to vehicle tires is defined as the“track free” time. Shorter track free times increase marking efficiencyby reducing or eliminating the need for traffic disruption through suchmeasures as closing lanes or placing traffic control devices to protectsuch markings.

U.S. Pat. No. 5,478,596 discloses liquid pavement marking compositionsthat solve many of the problems of alkyd-based and epoxy-based pavementmarking compositions. Such pavement marking compositions are preparedfrom a two part polyurethane-forming system of a first component havingisocyanate-reactive groups (a polyol) and a second component havingisocyanate groups. It is disclosed that such compositions dry faster,withstand weathering better, and do not discolor as readily asalkyd-based and epoxy-based compositions. However, the exemplifiedcompositions required aromatic isocyanates in combination with thepolyols and a catalyst. Any colorless or lightly colored aromaticpolyisocyanate is suggested to increase the reactivity and decrease theviscosity of the isocyanate component and provide a harder polyurethane.Aromatic isocyanates are not particularly desirable because theresultant polyurethanes are subject to environmental degradation anddiscoloration. Also, many lower molecular weight aromatic isocyanatesthat would decrease viscosity and modify reactivity or film propertiescan potentially pose significant inhalation risk or toxic hazard relatedto their vapor pressure. Furthermore, the use of catalysts is notdesirable because they can also catalyze degradation of thepolyurethanes. To overcome the deficiencies of aromatic isocyanates,aliphatic isocyanates could be used with polyols; however, this wouldrequire the use of a catalyst or an aromatic isocyanate together with analiphatic isocyanate to obtain sufficient rates of cure.

Thus, the need still exists for liquid pavement marking compositionsthat can simultaneously provide all of these features in a singlematerial: reduced environmental impact through formulations having lowvolatile organic content or that are substantially solvent-free;improved balance of coating rheology during application and filmformation to promote substrate wet out and fast cure to track-freefilms; broadened range of weather conditions for coating application;and improved marking performance through increased durability andretained reflectively. Especially needed are liquid pavement markingcompositions that resist shrinkage, thus avoiding cracking, coatingimperfections and failures.

SUMMARY OF THE INVENTION

We have discovered new secondary amines which react with isocyanates toform stable urea linkages. These amines may be produced cleanly viaMichael-type reaction of primary amines with variously substituted male(amide/esters) and fumar (amide/esters).

Accordingly, the present invention in its first aspect includes a novelsecondary amine of the formula shown here as formula (IV)

wherein X is alkyl, alkylene, aryl or arylene with a valency of n; R₁,R₂, R₄ and R₅ are each independently H, alkyl or aryl; R₃ is alkyl oraryl; and n is an integer greater than or equal to 1.

A second aspect of the present invention includes an improved processfor preparing amide-ester precursors of the formula (V), shown below,using an organic tin salt as a catalyst.

A third aspect of the present invention is a polyurea coatingcomposition derived from a polyisocyanate component and anisocyanate-reactive component which includes at least one compoundcorresponding to the novel secondary amines of the present invention.

A fourth aspect of the present invention includes a process of preparinga polyurea coating. This process consists of coating a substrate with apolyisocyanate component and an isocyanate-reactive component whichincludes at least one compound corresponding to the novel secondaryamines of the present invention and then hardening said composition at atemperature ranging from 10° C. to 80° C.

The present invention provides also a two-part liquid pavement markingincluding a binder having polyurea groups, wherein the binder isprepared from a two-part coating composition containing an aminecomponent including one or more secondary amines as defined above andoptionally one or more amine-functional coreactants, and an isocyanatecomponent comprising one or more polyisocyanates. Preferably, thepavement marking includes a binder having urea groups, wherein thebinder is prepared from a two-part coating composition containing anamine component including one or more secondary amines as defined aboveand optionally one or more amine-functional coreactants, and anisocyanate having one or more polyisocyanates, wherein the coatingcomposition has a minimum application temperature of at least about 10°C. and a track free time of no greater than about 5 minutes. Alsoprovided is a traffic bearing surface having thereon such a pavementmarking, and a pre-formed pavement marking wherein the composition iscoated on a substrate that can be applied to a traffic bearing surface.

Methods of applying such compositions are also provided. For example, amethod of marking a traffic bearing surface is provided. The methodincludes applying to the traffic bearing surface a two-part coatingcomposition containing an amine component including one or moresecondary amines and optionally one or more amine-functionalcoreactants, and an isocyanate component having one or morepolyisocyanates.

DETAILED DESCRIPTION OF THE INVENTION

The secondary amines of the invention are those of formula (IV)

wherein X is alkyl, alkylene, aryl or arylene with a valency of n; R₁,R₂, R₄ and R₅ are each independently H, alkyl or aryl; R₃ is alkyl oraryl; and n is an integer greater than or equal to 1.

An alkyl group is a paraffinic hydrocarbon group which is derived froman alkane by removing one hydrogen from the formula. The hydrocarbongroup may be either linear, branched or cyclic when R₁ and R₂ are takentogether with the nitrogen atom, having 1 to 20 carbon atoms.Preferably, the hydrocarbon has 1 to 5 carbon atoms. Simple examplesinclude methyl (—CH₃) and ethyl (—CH₂CH₃).

An aryl group is an unsaturated hydrocarbon group having an aromaticring structure characteristic of benzene, naphthalene, etc. i.e., eitherthe six carbon ring of benzene or the condensed six carbon rings ofother aromatic derivatives. The aromatic ring can be either substitutedor unsubstituted. Possible substituent groups include alkyl, amino,nitro, hydroxyl, halogen and methoxy groups. A simple example of an arylgroup (unsubstituted) is phenyl (—C₆H₅).

An isocyanate group is a compound containing the isocyanate radical(—NCO). The term isocyanate refers to a polyisocyanate, preferably adiisocyanate or triisocyanate.

An arylene group is a multivalent radical which is formed by removinghydrogen from at least two carbon sites on an aromatic nucleus.

An alkylene group is an organic radical which is formed by removinghydrogen from at least two carbon sites on an aliphatic hydrocarbon. Asimple example is the ethylene radical, —C₂H₄—.

As discussed previously, the novel secondary amines of the presentinvention may be produced via Michael-type reaction of primary amineswith various amide-esters. Useful Michael receptors as precursorsinclude adducts of alcohols with isomaleimides. This reaction isillustrated below providing a compound of formula (V).

The use of an organotin salt as a catalyst has resulted in increasedyields of desired product. The process of the present invention includesreacting the above isomaleimide with an alcohol, R₃OH, in the presenceof an organotin catalyst to afford a compound of formula V, wherein R₂is an alkyl group or an aryl group and R₃, R₄, and R₅ are as definedabove.

The reaction of the isomaleimide with an alcohol can be carried out atfrom about 0° C. to about 100° C., preferably from ambient temperatures,about 25° C. to about 70° C. Examples of organotin salts employable ascatalysts are dibutyltin dilaurate, dibutyltin diacetate, dimethyltindilaurate, stannous octoate, bis(lauryldibutyltin) oxide, dibutyltindimercaptide, and dibutyltin dimercaptide. A preferred catalyst isdibutyltin diacetate. The amount of catalyst used may vary from about0.1 to about 10 mole % based on the amount of alcohol. The isomaleimidestarting materials can be prepared by known methods.

An alternate method of preparing amide ester precursors includesreacting a maleic anhydride with an amine followed by converting thecarboxylic acid group to the desired ester. This reaction is illustratedbelow.

wherein R₁, R₂, R₃, R₄ and R₅ are as defined above, and Hal represents ahalide ion, preferably iodide.

The reaction of a primary amine with an amide-ester Michael receptor isoften spontaneous, rapid, and nearly quantitative. The adducts may besynthesized by simply allowing mixtures of primary amines and Michaelreceptors to stand for about 96 hours at about 70° C. in the absence ofcatalyst. This reaction is illustrated below.

wherein X, n and R₁ to R₅ are as defined above.

Amines useful in preparing the secondary amines of the present inventioninclude, for example, ethylene diamine, 1,2-diaminopropane,2,5-diamino-2,5-dimethylhexane, 1,11-diaminoundecane,1,12-diaminododecane, 2,4′-diamino-dicyclohexyl methane,1-amino-3,3,5-trimethyl-5-aminomethylcyclohexane, 2,4- or2,6-diaminotoluene, 2,4′- or 4,4′-diaminodiphenyl methane or mixturesthereof. Amines preferred for preparing the novel secondary amines ofthe present invention include 1,4-diaminobutane 1,6-diaminohexane,2,4,4-trimethyl-1,6-diaminohexane,1-amino-3,3,5-trimethyl-5-aminomethyl-cyclohexane,4,4′-diamino-dicyclohexyl methane,3,3-dimethyl-4,4′-diamino-dicyclohexyl methane or mixtures thereof.Especially preferred amines include 4,4′-methylene-bis(cyclohexylamine),2-methyl-1,5-pentanediamine, 1,6-diaminohexane and mixtures thereof.

The reaction generally proceeds to 80-99% completion within 96 hours.Since the reactions are clean, purification of the reaction products isnot necessary.

These sterically-hindered secondary amines react more controllably withelectrophiles than do the corresponding primary amines and hydrogenbonding in their adducts is significantly reduced or eliminated. Thenovel secondary amines of the present invention react with isocyanatesto form urea-amide/ester linkages. This reaction is illustrated below asformula (VII).

wherein X, R₁, R₂ and R₃ are as defined above and Y is X.

Unlike the urea-diester linkages, urea-amide/ester linkages are stable.The amide-ester resists cyclizing to a hydantoin. Hydantoins causeshrinkage and are formed as previously described with urea-diesterlinkages.

Polyurea Coatings

The present invention is further directed to a polyurea coatingcomposition which has a polyisocyanate component and anisocyanate-reactive component which contains at least one compoundcorresponding to the novel secondary amines of the present invention asdefined above. The cross-linking which takes place in the processaccording to the present invention is based on an addition reactionbetween the polyisocyanate component and the isocyanate-reactivecomponent, in particular the novel secondary amines of the presentinvention.

Polyisocyanates include compounds bearing at least one isocyanate groupand include known polyisocyanates of polyurethane chemistry. Suitablelow molecular weight polyisocyanates having a molecular weight between168 and 5000 include hexamethylene diisocyanate, 2,2,4- and/or2,4,4-trimethyl-1,6-hexamethylene diisocyanate, dodecamethylenediisocyanate, 1,4-diisocyanatocyclohexane,1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (IPDI), 2,4′-and/or 4,4′-diisocyanato-dicyclohexyl methane, 2,4′- and4,4′-diisocyanato-diphenyl methane and mixtures of these isomers withtheir higher homologues which are obtained by the phosgenation ofaniline/fornaldehyde condensates, 2,4- and/or 2,6-diisocyanatotolueneand any mixtures of these compounds.

It is preferred, however, to use derivatives of these monomericpolyisocyanates. These derivatives include polyisocyanates containingbiuret (carbamylurea) groups as described, for example, in U.S. Pat.Nos. 3,124,605, 3,201,372 DE-OS 1,101,394; polyisocyanates containingisocyanurate groups as described, for example, in U.S. Pat. No.3,001,973, DE-PS 1,022,789, 1,333,067 and 1,027,394 and DE-OS 1,929,034and 2,004,048; polyisocyanates containing urethane groups as described,for example, in DE-OS 953,012, BE-PS 752,261 and U.S. Pat. Nos.3,394,164 and 3,644,457; polyisocyanate containing carbodiimide groupsas described in DE-OP 1,092,007, U.S. Pat. No. 3,152,162 and DE-OS2,504,400, 2,537,685 and 2,552,350; and polyisocyanates containingallophanate groups as described, for example, in GB-PS 994,890, BE-PS761,626 and NL-OS 7,102,524.

The modified polyisocyanates are particularly preferred:N,N′,N″tris-(6-isocyanatohexyl)-biuret and mixtures thereof with itshigher homologues and N,N′,N″tris-(6-isocyanatohexyl)-isocyanurate andmixtures thereof with its higher homologues containing more than oneisocyanurate ring.

Isocyanate group-containing prepolymers and semi-prepolymers based onthe monomeric simple or modified polyisocyanates exemplified above andorganic polyhydroxyl compounds are also preferred for use as thepolyisocyanate component. These prepolymers and semi-prepolymersgenerally have about 140-8400 equivalent weight, preferably about210-420 equivalent weight, and are prepared in known manner by thereaction of the above mentioned starting materials at an NCO/OHequivalent ratio of about 1.05:1 to 10:1 preferably about 1.1:1 to 3:1,this reaction being optionally followed by distillative removal of anyunreacted volatile starting polyisocyanates still present.

The prepolymers and semi-prepolymers may be prepared from low molecularweight polyhydroxyl compounds having a molecular weight of 62 to 299,such as ethylene glycol, propylene glycol, trimethylol propane,1,6-dihydroxy hexane; low molecular weight, hydroxyl-containing estersof these polyols with dicarboxylic acids of the type exemplifiedhereinafter; low molecular weight ethoxylation and/or propoxylationproducts of these polyols; and mixtures of the preceding polyvalentmodified or unmodified alcohols.

The prepolymers and semi-prepolymers are, however, preferably preparedfrom the known relatively high molecular weight polyhydroxyl compoundsof polyurethane chemistry which have a molecular weight of 300 to about8000, preferably about 1000 to 5000, as determined by the functionalityand the OH number. These polyhydroxyl compounds have at least twohydroxyl groups per molecule and generally have a hydroxyl group contentof about 0.5 to 17% by weight.

Examples of suitable relatively high molecular weight polyhydroxylcompounds which may be used for the preparation of the prepolymers andsemi-prepolymers include the polyester polyols based on the previouslydescribed low molecular weight, monomeric alcohols and polybasiccarboxylic acids such as adipic acid, sebacic acid, phthalic acid,isophthalic acid, tetra-hydrophthalic acid, hexahydrophthalic acid,maleic acid, the anhydrides of these acids and mixtures of these acidsand/or acid anhydrides. Hydroxyl group-containing polylactones,especially poly-e-caprolactones, are also suitable for the preparationof the prepolymers and semi-prepolymers.

Polyether polyols, which are obtained in known manner by thealkoxylation of suitable starting molecules, are also suitable for thepreparation of the isocyanate group-containing prepolymers andsemi-prepolymers. Examples of suitable starting molecules for thepolyether polyols include the previously described monomeric polyols,water, organic polyamines having at least two NH bonds and any mixturesof these starting molecules. Ethylene oxide and/or propylene oxide areparticularly suitable alkylene oxides for the alkoxylation reaction.These alkylene oxides may be introduced into the alkoxylation reactionin any sequence or as a mixture.

Also suitable for the preparation of the prepolymers andsemi-prepolymers are the hydroxyl group-containing polycarbonates whichmay be prepared by the reaction of the previously described monomericdiols with phosgene and diaryl carbonates such as diphenyl carbonate.

These other optionally used isocyanate-reactive compounds are preferablyorganic polyhydroxyl compounds known from polyurethane chemistry andinclude both the low molecular weight polyhydroxyl compounds and therelatively high molecular weight polyhydroxyl compounds previously setforth for the preparation of the prepolymers and semi-prepolymerssuitable for use as the polyisocyanate component.

Isocyanate-reactive compounds which may be used as a portion of thepolyisocyanate component are the hydroxy functional polyacrylates knownfor use in polyurethane coatings. These compounds arehydroxyl-containing copolymers of olefinically unsaturated compoundshaving a number average molecular weight (M_(n)) determined by vaporpressure or membrane osmometry of about 800 to 50,000, preferably about1000 to 20,000 and more preferably about 5000 to 10,000, and having ahydroxyl group content of about 0.11 to 12% by weight, preferably about1 to 10% by weight and most preferably about 2 to 6% by weight. Thecopolymers are based on olefinic monomers containing hydroxyl groups andolefinic monomers which are free from hydroxyl groups. Examples ofsuitable monomers include vinyl and vinylidene monomers such as styrene,α-methyl styrene, o- and p-chloro styrene, o-, m- and p-methyl stryene,p-tert-butyl styrene; acrylic acid; (methy)acrylonitrile; acrylic andmethacrylic acid esters of alcohols containing 1 to 8 carbon atoms suchas ethyl acrylate, methyl acrylate, n- and isopropyl acrylate, n-butylacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, iso-octylacrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylateand iso-octyl methacrylate; diesters of fumaric acid, itatonic acid ormaleic acid having 4 to 8 carbon atoms in the alcohol component;(methy)acrylic acid amide; vinyl esters of alkane monocarboxylic acidshaving 2 to 5 carbon atoms such as vinyl acetate or vinyl propionate;and hydroxyalkyl esters of acrylic acid or methacrylic acid having 2 to4 carbon atoms in the hydroxyalkyl group such as 2-hydroxyethyl-, 2,hydroxypropyl-, 4-hydroxybutyl-acrylate and methacrylate and trimethylolpropane-mono- or pentaerythritomono-acrylate or methyacrylate. Mixturesof the monomers exemplified above may also be used for the preparationof the hydroxy functional polyacrylates. Mixtures of the polyhydroxylcompounds previously described may be used as a portion of thepolyisocyanate component.

In the coating compositions to be used for the process according to theinvention, the ratio by weight of the total quantity of bindercomponents to the quantity of solvent is about 40:60 to 100:0,preferably about 60:40 to 100:0.

The coating compositions to be used for the process according to theinvention may also contain other auxiliary agents and additivesconventionally used in polyurethane coatings, in particular pigments,fillers, leveling agents, catalysts, antisettling agents, antioxidants,UV stabilizers and the like.

The properties of the coatings obtained by the process according to theinvention may be adjusted, in particular by suitable choice of thenature and proportions of the starting components. Thus, for example,the presence of relatively high molecular weight, linear polyhydroxylcompounds either in the prepolymers or semi-prepolymers of eachcomponent increases the elasticity of the coatings; whereas, the absenceof such starting components increases the crosslinking density andhardness of the resulting coatings.

For carrying out the process according to the invention, the coatingcompositions to be used according to the invention are applied as one ormore layers to substrates by known methods such as spraying, brushcoating, immersion or flooding or by means of rollers or doctorapplicators. The process according to the invention is suitable for thefonnation of coatings on any substrates, e.g., metals, plastics, wood orglass. The substrates to be coated by the process according to theinvention may be treated with suitable primers before the processaccording to the invention is carried out.

After the substrates exemplified above have been coated, the coatingsare cured by the process according to the invention at a temperature ofabout −20° to 100° C. Curing is preferably carried out at a temperatureof about 10° C. to 80° C.

Liquid Pavement Marker

The present invention provides a two-part liquid pavement markingcontaining a binder having polyurea groups, wherein the binder isprepared from a two-part coating composition having an amine componentincluding one or more novel secondary amines of the present invention asdefined above and optionally one or more amine-functional coreactants,and an isocyanate component having one or more polyisocyanates.Preferably, the pavement marking contains a binder having urea groups,wherein the binder is prepared from a two-part coating compositionhaving an amine component with one or more secondary amines andoptionally one or more amine-functional coreactants, and an isocyanatecomponent containing one or more polyisocyanates, wherein the coatingcomposition has a minimum application temperature of at least about 10°C. and a track free time of no greater than about 5 minutes.

In the binders used according to the invention, there is an equivalentratio of isocyanate groups to isocyanate-reactive groups of about 0.8:1to 20:1, preferably about 0.8:1 to 2:1, more preferably about 0.8:1 to1.2:1 and most preferably about 1:1. The optional polyhydroxyl compoundis present in the amine component in an amount such that up to 20hydroxyl groups are present for each secondary amino, preferably theequivalent ratio of hydroxyl groups to secondary amino groups is about10:1 to 1:10.

The binders to be used according to the invention are prepared by mixingthe individual components together. Preparation of the binders iscarried out solvent-free or in the presence of the solventsconventionally used in polyurethane coatings. It is an advantage of theprocess according to the invention that the quantity of solvent used maybe greatly reduced when compared with that required in knowntwo-component systems.

Examples of suitable solvents include xylene, butyl acetate, methylisobutyl ketone, methoxypropyl acetate, N-methyl pyrrolidone, petroleumhydrocarbons, iso-butanol, butyl glycol, butyoxyethanol, chlorobenzenesand mixtures of such solvents. The alcoholic solvents previouslymentioned may be used, provided that the optional polyhydroxyl compoundsare not used.

The pavement marking compositions of the present invention contain abinder having urea groups. This binder is prepared from a two-partsystem that includes an amine compound and an isocyanate component.Preferably, the amine component includes secondary amines. Morepreferably, the amine component includes the secondary amine of thepresent invention. Most preferably, the amine component includes one ormore amide-ester amines, optionally blended with one or moreamine-functional coreactants other than an amide-ester amine.Preferably, the amine-functional coreactants are polymeric polyamines,and more preferably, substantially polymeric diamines. Theseamine-functional coreactants are selected to balance the properties ofthe coating during the curing process and in its final form.

The amine and isocyanate components are chosen such that the resultantpavement marking is generally resistant and durable to environmental andvehicular stresses and has good daytime visibility. Preferably, it alsohas good night-time visibility. Durability can be evidenced by goodadhesion (i.e., anchoring) to a wide variety of substrate surfaces,including concrete, asphalt, and other markings, whether they bemarkings of the same or different material. It can also be evidenced bygood adhesion (i.e., anchoring) of reflective elements to the marking,if they are used. As used herein, “durability” can be determined byapplying the pavement marking to a road surface that will be exposed totraffic conditions and monitoring the performance of the marking overtime. Reflectivity and whiteness can be measured instrumentally in thefield and the resistance of the marking to wear and erosion can besubjectively evaluated. Durable markings have continued presence on thesubstrate, good visibility, and, preferably, good reflectivity over anextended length of time.

The pavement markings formed from the composition of the presentinvention preferably are durable (i.e., have a useful life) for at leastabout two years, more preferably, for at least about three years, andmost preferably, for at least about four years. If reflective elementsare used, the pavement markings have a retained reflectivity of at leastabout 100 mcd/m²/lux, and more preferably, at least about 150mcd/m²/lux, throughout its useful life. As used herein, “retainedreflectivity” is used to describe the effectiveness of maintainedretroreflective performance of a pavement marker over its useful life.Retroreflectivity is currently typically measured by an instrument inthe laboratory at fixed entrance and observation angles, according toASTM D 4061-94. Recent work (Transportation Research Record 1409published 1994 by the Transportation Research Board) has shown that theentrance angle at which light is incident and observation angles fromwhich a driver actually views a pavement marking, referred to herein as“approximate driver geometries,” are appropriate for measuredretroreflective performance of pavement markings.

The amine and isocyanate components are preferably chosen such that thepavement marking composition:

(1) is a liquid with a high solids content (preferably, at least about75 wt-%, and more preferably, at least about 90 wt-%, based on the totalweight of the composition), which is substantially solvent free(preferably, less than about 5 wt-% solvent, based on the total weightof the composition);

(2) has a rapid cure profile, with a track-free time (i.e., a dry timeat ambient roadway conditions when the coating is applied) ofpreferably, no greater than about five minutes, more preferably nogreater than about four minutes, and most preferably, no greater thanabout three minutes, and a useful open time (i.e., the length of timethe composition will remain free flowing after application to a surfacefor adequate substrate wet out and particle or reflective elementwicking/anchorage) preferably, an open time of at least about 30seconds, and more preferably, at least about one minute;

(3) has a broad application window (i.e., it is able to be applied overa wide range of temperatures, with emphasis on use at lowertemperatures) preferably, having a minimum application temperature of atleast about 45° F., more preferably, at least 40° F., even morepreferably, at least about 35° F., and most preferably, at least about25° F.;

(4) is compatible with two-part static mix or airless high pressureimpingement-mix application equipment;

(5) includes commercially available, low-cost raw materials; and

(6) is generally storage stable preferably, having a useful shelf-lifeof at least six months, more preferably, at least one year, and mostpreferably, at least two years.

Although the pavement marking compositions of the present invention arereferred to as two-part systems, a number of additives may also beincluded. These additives include weathering additives, antioxidants,dispersion and grinding aids, wetting agents, impact modifiers,defoamers, pigments, fillers, extenders, diluents, plasticizers,leveling agents and surfactants.

Pigments are well known in the pavement marking art to impart desiredvisual appearance properties during the daytime and contribute to thereflective properties of the marking at night. Fillers and extenders canbe used to modify flow properties of the liquid coating and cancontribute to the bulk volume of the final coating. Fillers may also beused to achieve a particular volume ratio without significantlyaffecting the reactive chemistry. The pigments, fillers and extenderscan have a significant impact on uncured formulation and cured filmdensity, film cure profile and track free time, cured film modulus,coating adhesion to a substrate, response to thermal cycling, abrasionand coating durability.

Traffic-Bearing Surfaces

A method of marking a traffic bearing surface is provided, whichincludes applying to the traffic bearing surface a two-part coatingcomposition containing an amine component having one or more of thenovel secondary amines of the present invention as defined above andoptionally one or more amine-functional coreactants, and an isocyanatecomponent containing one or more polyisocyanates.

The two-part coating composition is typically applied using spraycoating techniques. Typically, the two components are applied using aspray apparatus which allows mixing immediately prior to exiting fromthe apparatus. For example, two-component, high pressure, airless,impingement mixing systems can be used.

An example of an airless, impingement mixing spray system ismanufactured by Gusmer. The system includes the following components: aproportioning section which meters the components and raises thepressure above about 1500 psi; a heating section to control theviscosity of each component; and an impingement spray gun which combinesthe two components and allows mixing just prior to atomization.

Another useful system is similar to the impingement unit, except that ituses a static mix tube to achieve blending of the two components. Thismix tube contains a number of flights designed to mix the componentsprior to atomization.

It should be noted that the liquid pavement marking compositions providepolyurea coatings having conventional daytime visibility. They can alsofunction as binders to anchor reflective optical elements. When thereflective elements are glass or ceramic microspheres, they aretypically in the range of about 200 μm to about 600 μm and may beincorporated into the coating, or preferably, may be dropped onto thewet coating.

Post-spray applied elements in the form of glass or ceramic microspherescan also be used as a binder filler in addition to providing night timereflectivity. They may function similarly to mineral particulates on thewear surface. Preferably, typical coverage rates are greater than about4 pounds of glass beads per gallon of paint, more preferably greaterthan 10 pounds per gallon, even more preferably greater than 25 poundsper gallon and most preferably, greater than 30 pounds per gallon.

WORKING EXAMPLES Preparation of tert-Butylisomaleimide

(Z)-4-(tert-Butylamino)-4-oxo-2-butenoic Acid

To a 12L four necked round bottom flask with a mechanical stirrer,thermometer and an addition funnel, under nitrogen, was added 1072.6grams of maleic anhydride (10.9 moles) and 6062 grams of acetonitrile.The mixture was stirred to dissolve the solids and cooled to −7° C. Tothis was added 800 grams of t-butylamine (10.9 moles) slowly at a ratesuch that the temperature remained below 0° C. (approximately 2.5 houraddition). Following the addition the mixture was stirred at −7° C. forone hour and overnight at room temperature. The solid was collected byfiltration, washed with 500 mL of acetonitrile and dried to give 1355grams of (Z)-4-(tert-butylamino)-4-oxo-2-butenoic acid as a white solid.13-C NMR shows this to be 94.62 wt %(Z)-4-(tert-butylamino)-4-oxo-2-butenoic acid, and 5.38 wt %t-butylamine. This material was used without further purification forthe next reaction.

5-(tert-Butylamino)-2,5-dihydro-2-furanone

To a 12 liter four necked round bottom flask with a mechanical stirrer,thermometer, addition funnel and condenser, under nitrogen, was added700 grams of (Z)-4-(tert-butylamino)-4-oxo-2-butenoic acid (4.0 moles)and 7757 grams of dichloromethane. The mixture was cooled to −5° C. and438.6 grams of ethyl chloroformate (4.0 moles) was added. The mixturewas cooled to −10° C. and 408.9 grams of triethylamine (4.0 moles) wasadded slowly at a rate such that the temperature remained below −7° C.Stirring was continued at −5° C. for 2.5 hours during which time theevolution of carbon dioxide was observed. The mixture was warmed to 11°C. and a premix of 272 grams of sodium bicarbonate dissolved in 3640grams of distilled water was added. The mixture was stirred for 10minutes, phase split, and the aqueous phase was removed. The organicphase was extracted three times with 3L each of distilled water. Theorganic phase was dried with 275 grams of sodium sulfate, filtered andthe solvent was removed in vacuo at 30° C. The residue was purified bydistillation (50° C., 0.05 mm Hg) to give 550 grams of5-(tert-butylimino)-2,5-dihydro-2-furanone. This material is hereinafterreferred to as tert-butylisomaleimide. 13-CNMR shows this to be greaterthan 99% pure.

Preparation of Amide/Ester #1

2.413 grams (40.1 meq.) of anhydrous 2-propanol (Aldrich, Milwaukee,Wis.) was combined with 0.056 grams (0.160 meq.) of dibutyltin diacetate(Air Products, Allentown, Pa.) and mixed for approximately 5 minutes.6.405 grams (40.1 meq.) of tert-butylisomaleimide was added and mixedfor four days at ambient conditions. The product was a low viscosity,clear, yellow colored liquid. ¹H-NMR indicated a yield of 97% of themale(amide-ester) product.

EXAMPLE 1 Preparation of Secondary Amine

0.777 grams (3.54 meq.) of amide-ester #1 was weighed into a vial. 0.372grams (3.54 meq.) 4,4′-methylenebis(cyclohexylamine) (PACM-20, AirProducts, Allentown, Pa.) was added to the amide-ester and mixed for 10minutes. The reaction mixtute was placed in a 70° C. oven for four days.The product was a viscous, clear, yellow colored liquid. ¹H-NMRindicated a yield of 90% of the desired amine product.

EXAMPLE 2 Preparation of Secondary Amine

0.999 grams (4.55 meq.) of amide-ester #1 was weighed into a vial. 0.264grams (4.54 meq.) 2-methyl-1,5-pentanediamine (Dytek A, DuPontChemicals, Wilmington, Del.) was added to the amide-ester and mixed for10 minutes. The reaction mixture was placed in a 70° C. oven for fourdays. The product was a viscous, clear, yellow colored liquid. ¹H-NMRindicated a yield of 88% of the desired amine product.

Preparation of Amide/Ester #2

193.50 grams (3.22 eq.) of anhydrous 2-propanol (Aldrich, Milwaukee,Wis.) was combined with 4.34 grams (12.4 meq.) of dibutyltin diacetate(Air Products, Allentown, Pa.) and mixed for approximately 5 minutes.480.00 grams (3.13 eq.) of tert-butylisomaleimide was added and mixedfor one day at ambient conditions followed by three days at 70° C. Theproduct was a low viscosity, clear, yellow colored liquid. ¹H-NMRindicated a yield of 98.6% of the male(amide-ester) product.

EXAMPLE 3 Preparation of Secondary Amine

4.927 grams (23.10 meq.) of amide-ester #2 (at 70° C.) was weighed intoa vial. 1.342 grams (23.10 meq.) 1,6-diaminohexane at 70° C. (Aldrich,Milwaukee, Wis.) was added to the amide-ester and mixed for 10 minutes.The reaction mixture was placed in a 70° C. oven for 40 hours. Theproduct was a clear, yellow colored liquid. ¹H-NMR indicated a yield of95.5% of the desired amine product.

Preparation of Amide/Ester #3

(Z)-4-oxo-4-Piperidino-2-butenoic Acid

To a 500 mL three necked round bottom flask with a mechanical stirrer,thermometer, and addition funnel, under nitrogen, was added 50 grams(0.51 mmol) of maleic anhydride and 363.7 mL of acetonitrile. Themixture was stirred at room temperature until the solid dissolved andthen cooled in an ice bath. To the solution was added 43.4 grams (0.51mmol) of piperidine at a rate such that the temperature did not go above20° C. The cooling bath was allowed to melt slowly and the mixture wasstirred overnight at room temperature. The solvent was removed in vacuoto give 95.7 grams of a brown solid. 13-C NMR shows this solid to be88.8 wt % (Z)-4-oxo-4-piperidino-2-butenoic acid, 3.4 wt % acetonitrile,2.2 wt % maleic anhydride, 4.4 wt % maleic acid and 1.2 wt % of thecorresponding fumarate amide or acid. This material was used in the nextstep without further purification.

Isopropyl (Z)-4-oxo-4-Piperidino-2-butenoate

To a 250 mL three necked round bottom flask, under nitrogen, was added40 grams (0.22 mmol) of (Z)-4-oxo-4-piperidino-2-butenoic acid and 800mL of acetonitrile. The mixture was stirred at room temperature todissolve the solid. To this was added 106.71 grams (0.33 mmol) of cesiumcarbonate and then 111.34 grams (0.66 mmol) of 2-iodopropane was addedover a three minute period. The mixture was heated to 80° C. for onehour and cooled to room temperature. To the mixture was added 350 mL ofwater and 250 mL of ethyl acetate. The mixture was stirred, phase splitand the organic phase was separated. The organic phase was extracted twotimes with 500 mL of water. The organic phase was dried over magnesiumsulfate, filtered, and the solvent was removed in vacuo to give 28 gramsof a brown liquid. This liquid was distilled on a Kugelrohr (105° C. airtemperature, 0.130 mTorr) to give 21.97 grams of a colorless liquid.13-CNMR shows this to be 94 wt % isopropyl(Z)-4-oxo-4-piperidino-2-butenoate, isopropyl(E)-4-oxo-4-piperidino-2-butenoate, and 2.5 wt % uncharacterizedimpurities.

EXAMPLE 4 Preparation of Secondary Amine

0.335 gram (5.766 meq.) of 1,6-diaminohexane (at 70° C., Aldrich,Milwaukee, Wis.) was weighed into a vial. 1.299 grams (5.766 meq.) ofamide-ester #3 (at 70° C.) was added to the amine and mixed for 10minutes. The reaction mixture was placed in a 70° C. oven for 40 hours.The product was a clear, yellow colored liquid. ¹H-NMR indicated a yieldof 90.2% of the desired amine product.

EXAMPLE 5

Approximately stoichiometric amounts, based on equivalent weights ofeach material of 4 different diisocyanates and the secondary amine, asdescribed in EXAMPLE 3 were used to prepare coating samples. Because ofthe rapid cure rate, the secondary amine was first weighed in a beaker.The diisocyanates were then added. The mixture was then vigorouslystirred for 15-30 seconds and poured quickly onto a surface to cure. Theresults are shown in the following table.

TABLE Cure Profile Amine Open Core- Equivalent Equivalent NCO Time Filmactant Weight Isocyanate Weight Index (Min) Properties EX 3 274 N-3300194 1.05 <0.5 High modulus, tough EX 3 274 N-3400 194 1.05 <0.5 Highmodulus, tough EX 3 274 Desmodur 131 1.05 <0.5 High W modulus, brittleEX 3 274 TMXDI 122 1.05 <0.5 High modulus, brittle EX 3 274 IPDI 1111.05 <0.5 High modulus, v. Brittle Raw Material Information: RawMaterial Supplier Product Description N-3300 Bayer Corp. Polyfunctionalaliphatic isocyanate resin based on hexamethylene diisocyanate N-3400Bayer Corp. Polyfunctional aliphatic isocyanate resin based onhexamethylene diisocyanate Desmodur W Bayer Corp. Hydrogenated MDI;H12MDI; dicyclohexylmethane, 4,4'- diisocyanate TMXDI Cytec IndustriesInc. Meta-tetramethylxylylene diisocyanate IPDI Aldrich Chemical Co.Isophorone Diisocyanate Inc.

The above specification, examples and data provide a completedescription of the manufacture and use of the composition of theinvention. Since many embodiments of the invention can be made withoutdeparting from the spirit and scope of the invention, the inventionresides in the claims hereinafter appended.

We claim:
 1. A secondary amine of the formula

wherein a) X is alkylene or arylene with a valency of n; b) R₁, R₂, R₄and R₅ are each independently selected from the group consisting ofhydrogen, alkyl and aryl; c) R₃ is either alkyl or aryl; and d) n is aninteger greater than one.
 2. The amine of claim 1, wherein n is 2 and Xis alkylene or arylene.
 3. The amine of claim 1, wherein R₁ is hydrogenor an alkyl of 1 to 5 carbon atoms, and R₂ is alkyl 1 to 5 carbon atomsor aryl.
 4. The amine of claim 1, wherein R₄ and R₅ are hydrogen.
 5. Theamine of claim 1, wherein X is a divalent hydrocarbon group obtained bythe removal of the amino groups from ethylene diamine,1,2-diaminopropane, 2,5-diamino-2,5-dimethylhexane,1,11-diaminoundecane, 1,12-diaminododecane, 2,4′-diamino-dicyclohexylmethane, 2,4- or 2,6-diaminotoluene, 2,4′- or 4,4′-diaminodiphenylmethane.
 6. The amine of claim 1, wherein X is a divalent hydrocarbongroup obtained by the removal of the amino groups from1,4-diaminobutane, 1,6-diaminohexane, 2,4,4-trimethyl-1,6-diaminohexane,1-amino-3,3,5-trimethyl-5-aminomethyl-cyclohexane,4,4′diamino-dicyclohexyl methane or3,3-dimethyl-4,4′-diamino-dicyclohexyl methane.
 7. The amine of claim 1,wherein R₁ is hydrogen, and R₂ is alkyl of 1 to 5 carbon atoms or aryl.8. The amine of claim 1, wherein R₁ and R₂ are both alkyl of 1 to 5carbon atoms.
 9. The amine of claim 7, wherein R₂ is tert-butyl and R₃is isopropyl.
 10. The amine of claim 1, wherein R₁ and R₂ taken togetherwith the nitrogen atom form a five or six-membered ring.
 11. The amineof claim 1, wherein X is a divalent hydrocarbon group obtained by theremoval of the amino groups from 4,4-methylene-bis(cyclohexylamine). 12.The amine of claim 1, wherein X is a divalent hydrocarbon group obtainedby the removal of the amino groups from 2-methyl-1,5-pentanediamine. 13.The amine of claim 1, wherein X is a divalent hydrocarbon group obtainedby the removal of the amino groups from 1,6-diaminohexane.
 14. Asecondary amine of the formula

wherein a) X is alkyl, alkylene, aryl or arylene with a valency of n; b)R₁, R₂, R₄ and R₅ are each independently selected from the groupconsisting of hydrogen, alkyl and aryl; c) R₃ is either alkyl or aryl;d) n is an integer greater or equal to one; e) R₁ is hydrogen; and f) R₂is alkyl of 1 to 5 carbon atoms or aryl.